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The medical applications of porous Mg scaffolds are limited owing to its rapid corrosion, which dramatically decreases the mechanical strength of the scaffold. Mimicking the bone ...structure and composition can improve the mechanical and biological properties of porous Mg scaffolds. The Mg structure can also be coated with HA by an aqueous precipitation coating method to enhance both the corrosion resistance and the biocompatibility. However, due to the brittleness of HA coating layer, cracks tend to form in the HA coating layer, which may influence the corrosion and biological functionality of the scaffold. Consequently, in this study, hybrid poly(ether imide) (PEI)–SiO2 layers were applied to the HA-coated biomimetic porous Mg to impart the structure with the high corrosion resistance associated with PEI and excellent bioactivity with SiO2. The porosity of the Mg was controlled by adjusting the concentration of the sodium chloride (NaCl) particles used in the fabrication via the space-holder method. The mechanical measurements showed that the compressive strength and stiffness of the biomimetic porous Mg increased as the portion of the dense region increased. In addition, following results show that HA/(PEI–SiO2) hybrid-coated biomimetic Mg is a promising biodegradable scaffold for orthopedic applications. In-vitro testing revealed that the proposed hybrid coating reduced the degradation rate and facilitated osteoblast spreading compared to HA- and HA/PEI-coating scaffolds. Moreover, in-vivo testing with a rabbit femoropatellar groove model showed improved tissue formation, reduced corrosion and degradation, and improved bone formation on the scaffold.
Porous Mg is a promising biodegradable scaffold for orthopedic applications. However, there are limitations in applying porous Mg for an orthopedic biomaterial due to its poor mechanical properties and susceptibility to rapid corrosion. Here, we strategically designed the structure and coating layer of porous Mg to overcome these limitations. First, porous Mg was fabricated by mimicking the bone structure which has a combined structure of dense and porous regions, thus resulting in an enhancement of mechanical properties. Furthermore, the biomimetic porous Mg was coated with HA/(PEI-SiO2) hybrid layer to improve both corrosion resistance and biocompatibility. As the final outcome, with tunable mechanical and biodegradable properties, HA/(PEI-SiO2)-coated biomimetic porous Mg could be a promising candidate material for load-bearing orthopedic applications.
Combination of bioactive material such as hydroxyapatite (HAp) with antibacterial agents would have great potential to be used as bone implant materials to avert possible bacterial infection that can ...lead to implant-associated diseases. The present study aimed to develop an antibacterial silver nanoparticle-decorated hydroxyapatite (HAp/AgNPs) nanocomposite using chemical reduction and thermal calcination approaches. In this work, natural HAp that was extracted from chicken bone wastes is used as support matrix for the deposition of silver nanoparticles (AgNPs) to produce HAp/AgNPs nanocomposite. XRD, FESEM-EDX, HRTEM, and XPS analyses confirmed that spherical AgNPs were successfully synthesized and deposited on the surface of HAp particles, and the amount of AgNPs adhered on the HAp surface increased with increasing AgNO
3
concentration used. The synthesized HAp/AgNPs nanocomposites demonstrated strong antibacterial activity against
Staphylococcus aureus
bacteria, where the antibacterial efficiency is relied on the amount and size of deposited AgNPs. In addition, the in vitro bioactivity examination in Hank’s balanced salt solution showed that more apatite were grown on the surface of HAp/AgNPs nanocomposite when AgNO
3
concentration used >1 wt.%. Such nanocomposite with enhanced bioactivity and antibacterial properties emerged as a promising biomaterial to be applied for dentistry and orthopedic implantology.
Metamaterials Liu, Ruopeng; Cui, Tie Jun; Smith, David R
2010, 2009, 20091005, 2009-11-15
eBook
Metamaterials:Theory, Design, and Applications goes beyond left-handed materials (LHM) or negative index materials (NIM) and focuses on recent research activity. Included here is an introduction to ...optical transformation theory, revealing invisible cloaks, EM concentrators, beam splitters, and new-type antennas, a presentation of general theory on artificial metamaterials composed of periodic structures, coverage of a new rapid design method for inhomogeneous metamaterials, which makes it easier to design a cloak, and new developments including but not limited to experimental verification of invisible cloaks, FDTD simulations of invisible cloaks, the microwave and RF applications of metamaterials, sub-wavelength imaging using anisotropic metamaterials, dynamical metamaterial systems, photonic metamaterials, and magnetic plasmon effects of metamaterials. TOC:Preface.- Acknowledgments.- Table of Contents.- List of Contributors.- Introduction to Metamaterials.- Optical Transformation Theory.- General Theory on Artificial Metamaterials.- Rapid Design of Metamaterials.- Broadband and Low-Loss Non-Resonant Metamaterials.- Experiment on Cloaking Devices.- Finite-Difference Time-Domain Modeling of Electromagnetic Cloaks.- Compensated Anisotropic Metamaterials: Manipulating Sub-Wavelength Images.- The Dynamical Study of Metamaterial Systems.- Photonic Metamaterials Based on Fractal Geometry.- Magnetic Plasmon Modes Introduced by the Coupling Effect in Metamaterials.- Enhancing Optical Coupling with Metamaterials.- Wideband and Low Loss Metamaterials for Microwave and RF Applications: Fast Algorithm and Antenna Design.- Experiments and Applications of Metamaterials in Microwave Regime.- Left-handed Transmission Line of Low Pass and Its Applications.- Glossary.- Index.
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Coatings based on ion-substituted calcium phosphate (Ca-P) have attracted great attention in the scientific community over the past decade for the development of biomedical ...applications. Among such Ca-P based structures, hydroxyapatite (HA) has shown significant influence on cell behaviors including cell proliferation, adhesion, and differentiation. These cell behaviors determine the osseointegration between the implant and host bone and the biocompatibility of implants. This review presents a critical analysis on the physical vapor deposition magnetron sputtering (PVDMS) technique that has been used for ion-substituted Ca-P based coatings on implants materials. The effect of PVDMS processing parameters such as discharge power, bias voltage, deposition time, substrate temperature, and post-heat treatment on the surface properties of ion-substituted Ca-P coatings is elucidated. Moreover, the advantages, short comings and future research directions of Ca-P coatings by PVDMS have been comprehensively analyzed. It is revealed that the topography and surface chemistry of amorphous HA coatings influence the cell behavior, and ion-substituted HA coatings significantly increase cell attachment but may result in a cytotoxic effect that reduces the growth of the cells attached to the coating surface areas. Meanwhile, low-crystalline HA coatings exhibit lower rates of osteogenic cell proliferation as compared to highly crystalline HA coatings developed on Ti based surfaces. PVDMS allows a close reproduction of bioapatite characteristics with high adhesion strength and substitution of therapeutic ions. It can also be used for processing nanostructured Ca-P coatings on polymeric biomaterials and biodegradable metals and alloys with enhanced corrosion resistance and biocompatibility.
Recent studies have utilized the physical vapor deposition magnetron sputtering (PVDMS) for the deposition of Ca-P and ion-substituted Ca-P thin film coatings on orthopedic and dental implants. This review explains the effect of PVDMS processing parameters, such as discharge power, bias voltage, deposition time, substrate temperature, and post-heat treatment, on the surface morphology and crystal structure of ion-substituted Ca-P and ion-substituted Ca-P thin coatings. It is revealed that coating thickness, surface morphology and crystal structure of ion-substituted Ca-P coatings via PVDMS directly affect the biocompatibility and cell responses of such structures. The cell responses determine the osseointegration between the implant and host bone and eventually the success of the implants.
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Recent advances in additive manufacturing (AM) have enabled the fabrication of functionally graded porous biomaterials (FGPBs) for application as orthopedic implants and bone ...substitutes. Here, we present a step-wise topological design of FGPB based on diamond unit cells to mimic the structure of the femoral diaphysis. The FGPB was manufactured from Ti-6Al-4V powder using the selective laser melting (SLM) technique. The morphological parameters, permeability and mechanical properties of FGPB samples were measured and compared with those of the biomaterials with uniform porous structures based on the same type of the unit cell. The FGPB exhibited a low density (1.9 g/cm3), a moderate Young’s modulus (10.44 GPa), a high yield stress (170.6 MPa), a high maximum stress (201 MPa) and favorable ductility, being superior to the biomaterials with uniform porous structures in comprehensive mechanical properties. In addition, digital image correlation (DIC) and finite element (FE) simulation were used to unravel the mechanisms governing the deformation and yielding behavior of these biomaterials particularly at the strut junctions. Both DIC and FE simulations confirmed that the deformation and yielding of the FGPB occurred largely in the load-bearing layers but not at the interfaces between layers. Defect-coupled FE models based on solid elements provided further insights into the mechanical responses of the FGPB to compressive loads at both macro- and micro-scales. With the defect-coupled representative volume element model for the FGPB, the Young’s modulus and yield stress of the FGPBs were predicted with less than 2% deviations from the experimental data. The study clearly demonstrated the capabilities of combined experimental and computational methods to resolve the uncertainties of the mechanical behavior of FGPBs, which would open up the possibilities of applying various porosity variation strategies for the design of biomimetic AM porous biomaterials.
Functionally graded bone scaffolds significantly promote the recovery of segmental bone defect. In the present study, we present a step-wise topological design of functionally graded porous biomaterial (FGPB) to mimic the structure of the femoral diaphysis. The Ti-6Al-4V FGPB exhibited a superior combination of low density, moderate Young’s modulus, high yield stress and maximum stress as well as favorable ductility. The biomechanical performance of FGPB was studied in both macro and micro perspectives. The defect-coupled model revealed the significant yielding in the load-bearing parts and the Young’s modulus and yield stress of the FGPBs were predicted with less than 2% deviations from the experimental data. The superiority of combined experimental and computational methods has been confirmed.
Advanced magnetic nanostructures is an emerging field in magnetism and nanotechnology, but the literature consists of a rich variety of original papers and parts of reviews and books whose scope is ...comparatively broad. This calls for a book with specific emphasis on state-of-the-art synthetic methods for fabricating, characterizing and theoretically modeling new magnetic nanostructures. This book is intended to provide a comprehensive overview of the present state of the field. Leading researchers world-wide have contributed a survey of their special ties to guide the reader through the exploding literature in nanomagnetic structures. The focus is on deliberately structured nanomagnets. It includes cluster assembled, self-organized and patterned thin films but excludes, for example, multilayered thin films. We target both industrial and academic researchers in magnetism and related areas, such as nanotechnology, materials science, and theoretical solid-state physics.
Fiberglass and Glass Technology: Energy-Friendly Compositions and Applications provides a detailed overview of fiber, float and container glass technology with special emphasis on energy- and ...environmentally-friendly compositions, applications and manufacturing practices which have recently become available and continue to emerge. Energy-friendly compositions are variants of incumbent fiberglass and glass compositions that are obtained by the reformulation of incumbent compositions to reduce the viscosity and thereby the energy demand. Environmentally-friendly compositions are variants of incumbent fiber, float and container glass compositions that are obtained by the reformulation of incumbent compositions to reduce environmentally harmful emissions from their melts. Energy- and environmentally-friendly compositions are expected to become a key factor in the future for the fiberglass and glass industries. This book consists of two complementary sections: continuous glass fiber technology and soda-lime-silica glass technology. Important topics covered include: o Commercial and experimental compositions and products o Design of energy- and environmentally-friendly compositions o Emerging glass melting technologies including plasma melting o Fiberglass composite design and engineering o Emerging fiberglass applications and markets Fiberglass and Glass Technology: Energy-Friendly Compositions and Applications is written for researchers and engineers seeking a modern understanding of glass technology and the development of future products that are more energy- and environmentally-friendly than current products. TOC:Commercial and Experimental Glass Fibers.- Composite Design and Engineering.- Glass Fibers for Printed Circuit Boards.- High Strength Glass Fibers and Markets.- Composition of Commercial Glasses.- Design of Energy Friendly Compositions.- Basics of Melting and Glass Formation.- Thermodynamics of Glass Melting.- Glass Melt Stability.- Plasma Melt Technology and Applications.
Magnesium (Mg) has a long history of investigation as a degradable biomaterial. Physicians first began using Mg for biomedical applications in the late 19th century. Experimentation continued with ...varying levels of success until the mid-20th century when interest in the metal waned. In recent years the field of Mg-based biomaterials has once again become popular, likely due to advancements in technology allowing improved control of corrosion. Although this has led to success in vascular applications, continued difficulties in predicting and controlling the corrosion rate of Mg in an intraosseous environment has impeded the development of Mg-based biomaterials for orthopedic applications. In this review, an initial summary of the basic properties and the physiological role of Mg are followed by a discussion of the physical characteristics of the metal which lend it to use as a degradable biomaterial. A description of the historical and modern applications for Mg in the medical field is followed by a discussion of the methods used to control and assess Mg corrosion, with an emphasis on alloying. The second part of this review concentrates on the methods used to assess the corrosion and biocompatibility of Mg-based orthopedic biomaterials. This review provides a summary of Mg as a biomaterial from a biological perspective.
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